Makefile: remove pointless conditional assignment in SunOS section

Makefile: remove pointless conditional assignment in SunOS section

It is true that NEEDS_RESOLV is needed on SunOS if NO_IPV6 is set since
hstrerror() resides in libresolv, but performing this test at its current
location is not very useful.  It will only have any effect if the user
modifies the make variables from the make command line, and will have no
effect if a config.mak file is used.  A better location for this
conditional would have been further down in the Makefile after the
config.mak and config.mak.autogen had been parsed.  Rather than adding
clutter to the Makefile for a conditional that will likely never be
triggered, just remove it, and any user on SunOS that manually sets NO_IPV6
can also set NEEDS_RESOLV.

Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: Junio C Hamano <gitster@pobox.com>